1. Field of the Invention
This invention relates to butterfly valves and particularly to butterfly valves as utilized for controlling the flow of fluids through three ports.
2. Description of the Prior Art
An earlier filed patent application Ser. No. 959,643, filed Nov. 13, 1978, now U.S. Pat. No. 4,202,398 discloses a three way butterfly valve which eliminates the need for a liquid bypass port in the block of an internal combustion engine. In addition, the three way butterfly valve closes tightly with virtually no leakage through the main passage when the automobile air conditioning system is set in the maximum air conditioning mode. The three way valve also incorporates a fluid flow restrictor to protect the automobile heater core from excessive liquid pressure.
A disadvantage of the above described valve is that the resilient seal around the periphery of the valve plate has a tendency to bind or stick against the inner surface of the flow passageway when rotated. A further disadvantage of the above described valve is the need to position the valve plate angularly and radially before attaching the valve plate to the engaging pin in the flow passageway.